The invention relates to the field of devices for optical, recording on a record carrier.
The invention relates to a device for writing information blocks in a track pattern on a record carrier of a writable type, which device is provided with a write unit for writing areas of the record carrier via (i.e. by using) a beam of electromagnetic radiation with marks representing the information blocks, and positioning means for positioning the write unit on depending on a track structure which indicates the position of the track pattern on the record carrier.
The invention also relates to a writable record carrier having a track pattern for writing information blocks, and a track structure which indicates the position of the track pattern.
The invention also relates to a method of writing information blocks in a track pattern on a record carrier of the writable type. Marks representing the information blocks are written in areas of the record carrier via a write unit and a beam of electromagnetic radiation. The write unit is positioned depending on a track structure which indicates the position of the track pattern.
The invention also relates to a reading device for information blocks represented by optically readable marks in a track pattern on a record carrier. The device is provided with a read unit for reading the marks via a beam of electromagnetic radiation, and apparatus for positioning the read unit on the basis of the marks.
A writing device, a method and a record carrier of the type described in the opening paragraph for writing information blocks are known from U.S. Pat. No. 4,901,300 (PHN 12.398). In the system described in that document, information blocks are written in a track pattern on the record carrier and represented by optically readable marks. The record carrier has a track structure in the form of a wobbling pregroove with a varying frequency which represents position information. The writing device has a write head for scanning the record carrier via a beam of electromagnetic radiation. The tracking signals are derived from reflected radiation, and apparatus for positioning the write head during scanning based on the position information. During scanning, a modulation in the tracking signals is produced by the wobble. This modulation includes the position information encoded therein, indicating the absolute position in the track with respect to the starting point of the area intended for information. The information blocks are written on the record carrier at a desired position in conformity with their address, while, if necessary, the write head is positioned via a jump to another radial position in the track on the basis of the position information. A record carrier may be partly written and then includes written areas in which marks are present, and unwritten areas in which only the track structure is present. Reading devices are known which derive the tracking signals and/or position information only from the marks. Those skilled in the art are directed to EP 9 328 240 regarding successive formatting. The above citations are hereby incorporated herein in whole by reference.
The inventor recognizes that no position information can be generated in unwritten areas, so that a partly written record carrier is not reliably readable.
It is an object of the invention to provide apparatus with which a partly written record carrier can be read in a more reliable manner.
In accordance with a first aspect of the invention, a writing device as described in the opening paragraph is therefore characterized in that the device is provided with status apparatus for generating status information which is indicative of the fact that at least one area of the record carrier has been written. The status information includes initial-area information which indicates the position of an uninterrupted written initial area which extends from the start of a track pattern area intended for writing information blocks.
In accordance with a second aspect of the invention, a record carrier as described in the opening paragraph is characterized in that the record carrier is provided with status information which indicates that at least one area of the record carrier has been written. The status information includes initial-area information which indicates the position of an uninterrupted written initial area which extends from the start of a track pattern area intended for writing information blocks.
In accordance with a third aspect of the invention, a method as described in the opening paragraph is characterized in that status information is generated which indicates that at least one area of the record carrier has been written. The status information includes initial-area information which indicates the position of an uninterrupted written initial area which extends from the start of a track pattern area intended for writing information blocks.
In accordance with a fourth aspect of the invention, a reading device as described in the opening paragraph is characterized in that the positioning apparatus are adapted (i.e. have structures to enable it) to position depending upon status information which indicates that at least one area of the record carrier has been written. The status information includes initial-area information which indicates an uninterrupted written initial area which extends from the start of a track pattern area intended for writing information blocks.
The inventive measures have, inter alia, the advantage that the reading device only needs to be adapted (i.e. structurally modified to enable it) in a limited way and does not need to be provided with complex means for regaining position information on the basis of the track structure.
An embodiment of the writing device according to the invention is characterized in that the device is provided with rewriting apparatus for rewriting, contiguously to the initial area, information blocks which are isolated from the initial area. This has the advantage that the isolated information blocks can be read with a simple, standard reading device because a copy is available within the initial area.
An embodiment of the reading device according to the invention is characterized in that the positioning apparatus are adapted to reject instructions for positioning outside the initial area. This has the advantage that the reading device prevents the read head from reaching an unwritten area whereby the reading device would come in an undefined state.
Those skilled in the art will understand the invention and additional objects and advantages of the invention by studying the description of preferred embodiments below with reference to the following drawings which illustrate the features of the appended claims: